1. Dispersive Comb-Spectrum Interferometer: Metrological Characterization
Wiroj Sudatham
Industrial Metrology Program
KMUTT
17/01/2006
Umberto Minoni, Luigi Rovati, M. Bonardi, and Franco Docchio (Owner)
IEEE TRANSACTION ON INSTRUMENTATION AND MEASUREMENT, VOL. 48, NO. 6, DECEMBER 1999

2. Objective & Scope Introduction to DSCI Principle of measurement
Analytical of uncertainty sources
Experimental Results
Modeling tools for nonincremental distance measurement
Low-cost implementation, using a commercial low-cost laser diode
Analytical uncertainty sources
Application for the development industrial sensors
4/7/2019
Seminar – S. Wiroj
DSCI - Introduction

3. Introduction Interferometer
Tools, widely used in nonincremental distance measurement
Many type (difference component)
Interference of light waves
Principle of superposition
Coherence light source
Light Sources (normally used laser)
4/7/2019
Seminar – S. Wiroj
DSCI - Introduction

4. Introduction Dispersive Comb Spectrum Interferometer - DCSI
Michelson’s Interferometer System
White Light (LD 670 nm)
Diffraction Grating
Littrow Configuration
4/7/2019
Seminar – S. Wiroj
DSCI - Introduction

5. Introduction
Why DCSI ?
Easy to optical setup and mechanical moving parts
Robust and reliable configurations
high-accuracy
Using a commercial low cost laser diode as the light source
4/7/2019
Seminar – S. Wiroj
DSCI - Introduction

6. Principle Of Measurement
Measurement Setup RM MM LD MM
BS1
CCD CC TC
BS2 L1 L2
Littrow Configuration DG
4/7/2019
Seminar – S. Wiroj
DSCI – Principle Of Measurement

7. Principle Of Measurement
The CCD Camera for the spectral component detection and transfer to computer
Littrow configuration exhibits adequate spectral resolution to study interference phenomena of each lasing modes
4/7/2019
Seminar – S. Wiroj
DSCI – Principle Of Measurement

8. The interference signal Simulated signal at the
Principle Of Measurement
Signal processing
The interference signal
before sampling
Simulated signal at the
output of the camera
The distance to be measured S can be evaluated by gauging the period Tcos
The sampling frequency is given by the spectral frequency of the lasing modes
4/7/2019
Seminar – S. Wiroj
DSCI – Principle Of Measurement

9. Uncertainty Sources Two main cases Light source and its controls
Line width of each lasing modes
The value of center frequency
Optical setup including the detection of the interference signal
Drift from the diffraction grating
Drift from the CCD detection
4/7/2019
Seminar – S. Wiroj
DSCI – Uncertainty Sources

10. not be easily calculated
Uncertainty Sources
Uncertainty Model
not be easily calculated
mapping optical freq onto the
time scale of the camera signal
Where, Assuming a negligible change of air refractive index
4/7/2019
Seminar – S. Wiroj
DSCI – Uncertainty Sources

11. Experiment Results Laser Characterization The best condition
Operating at 43 mA
Temperature in the range from 8 oC to 14 oC
4/7/2019
Seminar – S. Wiroj
DSCI – Experiment Results

12. Experiment Results Laser Characterization Fringes visibility
if not, no aliasing
phenomena are present
The range of measurement should be
Experiment result
4/7/2019
Seminar – S. Wiroj
DSCI – Experiment Results

13. Experimental Results Numerical Case Uncertainty Components=
Data be used
A numerical estimate of the measurement uncertainty
Used data from prototype implementation and
Laser source characterization
The combined uncertainty of the measuring range 800 mm corresponding to about 1.4 mm
4/7/2019
Seminar – S. Wiroj
DSCI – Experiment Results

14. Experiment Results Distance Measurements Operating at 8 oC 42 mA
Environment 22 oC
SD of error is 1.3 mm
Calibration a implementation of the system with
interferometer traced to international standard
The sensitivity to l0 , that the laser has a temperature coefficient of 0.39 nm/oC
4/7/2019
Seminar – S. Wiroj
DSCI – Experiment Results

15. Conclusion Supportable both theory and experimental results
Suitable to carry out measurement over up to about 1 mm
Uncertainty of 0.18%
Low-cost commercial source
Application for the development of industrial sensors.
4/7/2019
Seminar – S. Wiroj
DSCI – Conclusion

16. THANK YOU FOR ATTENTION.
THE END.
Presentation by S. Wiroj
Dispersive Come-Spectrum Interferometer: Metrological Characterization
AND
THANK YOU FOR ATTENTION.
Umberto Minoni, Luigi Rovati, M. Bonardi, and Franco Docchio (Owner)
4/7/2019
IEEE TRANSACTION ON INSTRUMENTATION AND MEASUREMENT, VOL. 48, NO. 6, DECEMBER 1999